A lead frame is used to mount semiconductor elements on a substrate. A semiconductor device is manufactured by mounting the semiconductor elements on die pads of the lead frame and then encapsulating the semiconductor elements and the lead frame with a resin material. For example, a lead frame used for a surface-mount type semiconductor device includes die pads, on which semiconductor elements are mounted, and outer leads, which function as external connection terminals of the semiconductor device. The outer leads are soldered to pads (mount subjects), which are formed on a substrate or the like (for example, refer to Japanese Laid-Open Patent Publication Nos. 2003-78097 and 10-74879).